Most MEMS devices are fabricated using techniques that leave the mechanical structures exposed after the fabrication process is completed. Open-die MEMS devices can be easily destroyed if their unprotected mechanical elements come in contact with a physical object, so physical protection can be important. MEMS are also very susceptible to degradation by small particles, water vapor, static friction and corrosion. As such, MEMS devices generally need microscopic protection and encapsulation.
The MEMS package creates an air or vacuum cavity over the MEMS active area without impeding its motion or function (e.g., deflection, tilt, slide, rotation, or vibration). Wafer-level packaging of MEMS represents a challenging and often costly task in micro-system manufacturing. MEMS packaging differs from traditional microelectronics packaging in that the encapsulating cover should generally not touch the micro-machined device. The packaging should protect the sensor while providing suitable electrical access to outside environment. Conventional MEMS packaging and fabrication techniques are often inadequate to meet the above described challenges. As such, a need exists for improved methods for fabricating and interfacing with MEMS devices.